Insulated electrical conductor



Aug 3, 1948. E. s. MccoNNELL. ETAL 2,446,292

INSULATED ELECTRICAL CONDUCTOR Filed June 8, 194,5

ANENY Patented Aug. 3, 1948 INSULATED ELECTRICAL CONDUCTOR Edmond s. McConnell, Scarborough, N. Y., and

Wlnfred K. Prlestley, West Barringto n, and

Victor F. Volk, Bristol, 8.11., assignors to United States Rubber Company, New York, N. Y., a corporation of New Jersey Application June 8,1945, SerialV No. 598,310

This invention relates to an insulated electrical conductor that is so constructed that it has an exceptionally small over-all diameter and light Vweight for its service conditions.

The present insulated electrical conductor may be used in many kinds of services but because of its light weight, small size and resistance to fire, solvents and the deteriorating effects of fungus, it is particularly well adapted for use in the wiring of aircraft.

One object of the present invention is to provide an insulated conductor that is highly resistant to an external flame and to internal heat from' an over-loaded conductor.

Another object is to provide an insulated conductor, that is lighter in weight and smaller in over-all diameter than the insulated conductors 'available heretofore for use in wiring aircraft.

Another object is to provide an insulated con ductor which will render satisfactory service under an extremely wide range of high and low temperatures and is capable of withstanding repeated cycles of high heat and extreme cold.

Another object is to provide an insulated conductor which is highly resistant to fungi, by selecting materials which are immune to fungi, or by completely enclosing any material subject to such attack with other resistant covering material.

Another object is to provide an insulated conductor which is highly resistant to the deteriorating influence of solvents such as gasoline, lubricating oil, ethylene glycol, fluids used in hydraulic systems, and fresh and salt water.

Another object is to provide an insulated conductor that is highly fiexible and has a tough smooth finish which together with its small diameter facilitates its installation.

Another object is to provide an insulated conductor which is so constructed that the insulation can be easily and quickly pushed back adjacent an end of the metal conductor to expose a short end portion of the bare conductor, without damaging or nicking the conductor. This permits an end of the conductor to be quickly exposed so that it can be soldered or otherwise attached to a terminal.

Another object is to provide an insulated conductor having a light color and smooth finish that will remain clean and thus facilitate identification of circuit markings printed or stenciled on the surface.

Another object is to provide an insulated electrical conductor that makes more effective use of the dielectric properties of fibre glass. Heretofore nbre glass has been used as an outer braid or covering because of its fire resisting qualities.

z Claims. (Cx. 114-120) However, fibre glass is very difficult to convert into a moisture resisting layer or covering and furthermore it has been found extremely susceptible to mechanical abrasion. In applying fibre glass next to the metallic conductor and subsequently covering it with an insulating and moisture resisting elastic jacket as herein disclosed it is no longer necessary to impregnate or moisture proof the insulating layer of fibre glass. Furthermore, by covering the metallic conductor with the fibers parallel as obtained by wrapping and serving. it is found that cutting and breaking of the glass and fibres is much diminished as compared with a braid wherein the fibres of glass cross over and under each other.

The insulated electrical conductor of the present invention may have a solid or stranded conductor, around which is placed one or more layers of fire and fungi resistant non-adhering material, such as a serving or wrapping, a tape, or a braid formed of non-combustible fibers such as fiber glass or asbestos. This serving is laid directly upon the metal conductor and can be slid appreciably thereon to expose a short end portion of the conductor when desired.

Over the fiber glass or other non-combustible layer is provided an insulating material forming an elastic jacket that has good resistance to moisture. The insulating jacket is preferably formed of polychloroprene latex (neoprene latex) which has good flame and fungi resistant properties, but may be formed of natural rubber or other rubber or rubber-like materials including the vinyl derivatives that are compounded to give them elastic properties.

However since the fiber glass layer is likely to have minute fibers extending radially from the surface thereof, it is desirable to cause these minute fibers to be held down before the plastic jacket is applied, in order to secure a maximum degree of dielectric strength from a minimum wall thickness of the plastic jacket. This may be done by applying a thin film of varnish or lacquer over the fiber glass before or after it is applied as a layer. Better results however are obtained by wrapping a layer of textile fibers such as cotton, rayon or nylon over the fiber glass layer, or by winding a thin tape of flexible plastic material such as Cellophane over the fiber glass.

The elastic jacket when formed of neoprene latex is preferably applied by the liquid-dipped method to insure that the coating will be disposed concentric to the metal conductor. A good practical form of apparatus for applying this latex jacket is disclosed in the Bartlett Patent No. 2,353,987 for Liquid applicator. However, the insulating jacket may be applied by extrusion,

'i'ollowing description when read in connection with the accompanying drawing illustrating one good practical embodiment of the invention. wherein:

Fig. 1 is a side elevation of an insulated electrical conductor constructed in accordance with the present invention and showing each insulating layer partly removed; and

Fig. 2 is an enlarged transverse sectional view taken on the line 2-2 of Fig. l.

The conductor it may be formed of a single wire but is -preferably formed of a number of strands of annealed copper and these strands are preferably tinned, as this will give a protruding bare end portion of the wire added protection and facilitate soldered connections. About the conductor i is wound a serving il of non-combustible material. This serving is preferably fformed of a number of parallel illaments or strands of ll-bre glass and is wound tightly around the conductor l@ but is not adhesively secured thereto, so that the serving may be slid back a short distance from an end of the wire l@ when it is desired to expose a short end por tion of the wire so that it can be secured to a contact member.

As above stated ne glass lbres are likely to protrude from the surface of the nbre glass layer il and if it is attempted to deposit an inE sulating material such as neoprene as a jaclret dlre'ctly over the layer il, these protruding fibres will extend into such jacket and reduce its dielectric strength. 'lhis dimculty may be overcome by applying a film of varnish or shellac over the layer il or to the liber glass before or after it is wound upon the conductor, but this makes it more diillcult to slip the layer li by a sliding movement back from an end of the oonductor it. Therefore a serving of cotton, rayon, nylon or other iibrous material is preferably wound over the layer il in the opposite direc= tion as shown in the drawing to form the second insulating layer i2. However this second layer may be wound in the same direction as the first layer. The cotton or rayon may be treated with a fungi resistant material before or after it is applied to increase the protection of the electric conductor from fungi. This second layer i2 holds down and covers the protruding bres of the layer il and provides a satisfactory surface to 4 underlying serving to any appreciable extent but will be bonded fIr-mly thereto.

It is desirable to provide the insulated electrical conductor of the present invention with a smoother and harder outer surface than is provided by neoprene. Therefore in accordance with the present invention the neoprene jacket I3 has deposited thereover a thin illm Il of a synthetic linear polyamide such as nylon. The nylon used for this purpose is preferably an alcohol soluble nylon such for example as is sold on the market under the designation of type 6B and which is made as defined by claim 8 of the patent to Brubaker et al., No. 2,285,009. This nylon solution is preferably applied over the neoprene jacket by employing the apparatus disclosed in the above cited Bartlett patent, as it is found that this causes the nylon illm to embrace the neoprene jacket tightly. The nylon which has high tensile strength appears to shrink about the jacket to hug it tightly. The alcohol used as a solvent for the nylon does not produce any harmful swelling of the neoprene. The nylon however may be otherwise applied. It may be desirable to add a white pigment or coloring matter to the nylon solution so as to give the finished insulated electric conductor any desired receive a jacket i3 of insulating rubber or other color which will facilitate identification of the same when installed. A white or light colored outer surface for the conductor affords the further advantage in that identification numbers printed or vstenciled thereupon will show up clearly.

is further disclosing the present invention. the following dimensions are given of one good practical construction that is now being manufactured for installation in aircrafts and which has an AN conductor size it, this being very nearly the same as A. W. G. size it.

@ver-all diameter Stranded conductor l0 .050 Fiber glass layer ll .055" Cotton layer i2 .,illiil'l Neoprene latex Jacket lll .089" Nylon nlm li .093"

Prior Commercial Constructi Present Construction on Size l Maximum Overall Weight lbs. Diam. 1000 it.

Weight lbs.

1 AN (Army-Na Conductor size which is ve near] the sem W. G. size. Vy) ry y o aan.

This table shows that the present construction is considerably smaller in diameter and lighter in weight than a representative prior construction that meets the same service conditions.

By employing a ilber glass layer II that is wound next to the conductor Il but is not adhesively secured thereto a lighter and more ilexible construction is secured than when the liber glass layer is impregnated with a bonding material. Furthermoreif all the other layers I 2, I2 and Il are destroyed by re the fiber glass layer II may still serve to insulate the conductor Il.

'I'he fibrous cover Il, as above stated, prevents ilbers from the cover II from entering the Jacket I3. It also increases the insulating properties of the covering materials, and it is protected from moisture by the jacket I3;

The jacket I3 when formed of neoprene latex will have excellent llame and moisture resisting properties and will be highly resistant to the deteriorating influences of solvents such as gasoline. lubricating oil, ethylene glycol, uids used in hydraulic systems, fresh water and salt water,

therewith but not bonded thereto, a serving of fibrous textile material wound over the libre glass so as to hold down stray glass libres, an elastic jacket formed of a homogeneous plastic having lgood resistance to iiame and moisture covering cellent abrasion, flame and moisture resisting all of which may be present at diilerent times to Y conductor wires installed in an airplane. Furthermore neoprene is well adapted to withstand cold temperatures.

The nylon illm Il has high tensile strength and provides the conductor with a tough, smooth outer surface of light color, so that the wire identiilcation numbers placed thereupon will show up clearly and will not be readily obscured by grease or dirt.

All of the covers II, I2, I2 and Il are so formed and applied that they aiiord the conductor Il excellent protection and insulation for the total thickness of the insulating material, and produce a highly exible insulated conductor. The in- A sulating material is suiiiciently comprensible as a whole to be readily pushed back from an end of the conductor Il to expose a short end portion so that it can be secured to a tenninal. This makes the use of a mechanical stripping tool which is likely to nick or otherwise injure the conductor I0 unnecessary.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

l. An insulated electrical conductor having excellent abrasion, llame and moisture resisting properties, comprising a metal conductor, a ribbon-like serving of n ber glass wound in short spirals about the conductor in direct mi.

properties, comprising a metal conductor, a ribbon-like serving of nbre glass wound in short spirals about the conductor in direct contact therewith but not bonded thereto, a serving of fibrous textile material wound over the bre glass so as to hold down stray glass fibres, a, jacket oi poly-chloroprene bonded to the textile serving, and a thin strong film of synthetic linear polyamide covering and snugly embracing said jacket and having an outside diameter that is less than twice the diameter of the bare metal conductor, whereby a well covered highly nexible conductor o1' excellent insulating properties is provided and the insulation adjacent an end can be readily slid back to expose a short portion of the conductor.

. EDMOND S. MQCONNELL. WINFRID K. ,PRIEB'I'IER VICTOR Il'. VOLK.

REFERENCES G'IED The following references are of record in the ille of` this patent:

UmmPATENTB Number Name Date 2,253,967 Carl et al Aug. 26, 1941 2,280,024 Hall et al Oct., 21, 1941 2.313,234 Gavitt Mar. 9, 1943 2,349,952 Fuller May 30, 1944 2,390,099 Slagter et al Nov. 27, 1945 FOREIGN PATENTE Number Country Date 565.354 Great Aw. 18. 1943 

